The ease with which small amounts of blood can be collected onto a filter paper and processed for testing has been of interest in utilizing dried-blood specimens in screening tests for blood-borne diseases such as acquired immunodeficiency syndrome. This technique provides distinct advantages over conventional techniques where access to refrigeration, centrifuges for blood separation, and large supplies of expensive disposal items are limited. Specimens of whole blood collected onto filter paper and dried are also easier and safer to ship than specimens collected by venipuncture.
Nationwide, human immunodeficiency virus type 1 (HIV-1) seroprevalence surveys using dried neonatal blood specimens are critical to estimating HIV-1 seroprevalence among childbearing women. However, the noninclusion of blood specimens deemed "quantity not sufficient" (QNS) for HIV-1 antibody testing potentially introduces bias. In HIV-1 seroprevalence surveys which utilize dried neonatal blood specimens, QNS rates can be reduced by the use of multiple 1/8 inch DBS to analyze specimens which are of insufficient quantity to test using a standard 1/4 inch punch. By lowering QNS rates, the use of multiple 1/8 inch blood spots can be an effective way of assuring the accuracy of HIV-1 seroprevalence estimates. Redus et al. ("Use of the 1/8 inch Punch Method to Reduce QNS Rates and Improve Seroprevalence Estimates in the Survey in Childbearing Women", Centers for Disease Control and Prevention, Atlanta, Ga.), Hoxie et al. ("Improving Estimates of HIV-1 Seroprevalence Among Childbearing Women: Use of Smaller Blood Spots", Am. J. Pub. Health, October 1992, Vol. 82, No. 10, pgs 1370-1373) and Tappin et al. ("Prevalence of Maternal HIV Infection in Scotland on Unlinked Anonymous Testing of Newborn Babies", The Lancet, Vol. 337, Jun. 29, 1991, pgs 1565-1567) have described the use of DBS less than 1/4 inch and the use of four 1/8 inch diameter punches in place of one 1/4 inch diameter punch when one 1/4 inch punch cannot be obtained.
The immunoassays designed to perform testing on patient samples are generally optimized for maximum detection of a minimal amount of a specific antibody in a given sample. Because of standard practice, these assays require a significant fraction, a 1/4 inch or multiple 1/4 inch punches of the DBS sample provided by a lay person. Therefore, more samples are required than can be provided by the standard-sized punch. Complete testing is not always possible using standard punch sizes. For example, enzyme immunoassays require elutions from separate DBS punches for testing and subsequent confirmatory assays require additional elutions from separate DBS punches.
The requirement of a 1/4 inch punch is a limitation on the rate of compliance as most lay people are only able to provide a DBS which would yield a smaller size punch than the required 1/4 inch punch. Moreover, because of the geometry of a circle, in order to obtain four 1/8 inch spots from one DBS, one would need at least one complete 1/2 inch DBS, or a mix of spots with varying diameters greater than 1/8 inch. In a clinical or hospital laboratory setting, this may be possible when obtaining samples from neonates. However, it is an impractical requirement from a lay person. Therefore, a method is required to punch a multitude of substandard size DBSs from the same DBS which would collectively be equivalent to the standard punch size required by a particular assay.